Microsoft paid billions for a license to Nokia's patents, but the company has made explicit that Nokia still owns the patents. The genius of this move is that it allows Microsoft to double down on its patent war with Android. Microsoft boasts that the majority of Android phones sold worldwide have already paid for a license to Microsoft patents. By 2011, patent licensing revenue exceeded Microsoft's revenue from Windows Phone.

Now, Nokia can go after Android phone makers for royalties - even ones that have already paid Microsoft.

If Nokia is no longer in the device business but is just licencing patents to others in that business, there is no difference vs. a patent troll.

Nokia has retained (and I'll state it again since apparently reading is difficult for some on this website) their R&D division, the people who come up with this stuff in the first place. They are still a practicing entity.

They will still sell products and services (HERE, NSN, etc.) but they will just not sell products and services related to patents they already invented. That doesn't make them an NPE.

It'd be different if a company bought all of Nokia's patents (without buying a single division) and then asserted them against everyone.

The problem with NPEs is that they are impervious to patent aggression. Nokia is not.

What is the difference between the 'creator' corporation selling patents to a patent troll and the 'creator' corporation selling all productive assets to another corporation leaving the original corp as a patent holding company?

There is a huge different. Nokia spent the research budget to develop and has retained what is likely to be the very division which invented the patented content.

But equally obviously, MS actually purchased a licence for the patents associated with Nokia's former device division. If those are useless to phones/devices, why would MS licence them when MS isn't in the network gear business?

I don't think I ever claimed they were useless to phones/devices, why are you asking pointless questions?

I said that most of the patents are for telecommunications, or a fruit of that labor. Meaning if you license an essential patent or a hardware patent from Nokia for being a consumer of something their networking unit has made (ie mobile broadband via NSN) then it doesn't mean that the patent was invented as a result of the device.